接种内生降解菌Stenotrophomonas pavanii DJL-M3对多菌灵胁迫下水稻根际微生态的影响

内生降解菌定殖可促进水稻中农药等有机污染物的降解代谢，研究功能内生菌对农药暴露下水稻根际微生态的影响，可为利用植物-微生物互作调控农作物农药残留及修复农田生态环境污染提供科学依据。以水稻根际土壤中的蚯蚓、土壤酶和微生物群落为研究对象，分析接种内生菌Stenotrophomonas pavanii DJL-M3对水稻根际微生态响应多菌灵胁迫的影响。结果表明：多菌灵暴露导致水稻根际土壤过氧化氢酶活性增强，脲酶和蔗糖酶活性被抑制；多菌灵污染可对水稻根际周围的蚯蚓造成氧化损伤，致使其体内丙二醛累积并诱导超氧化物歧化酶和乙酰胆碱酯酶过表达；多菌灵残留显著降低水稻根际土壤微生物群落的多样性与碳源代谢活性。接种内生降解菌S.pavanii DJL-M3促进了水稻根际残留多菌灵的降解，缓解根际土壤微生物与蚯蚓所受胁迫压力，显著提高了土壤脲酶、蔗糖酶活力以及蚯蚓的存活率，并有效提升了水稻根际微生物群落的代谢活性与多样性。因此，接种内生降解菌S.pavanii DJL-M3有助于多菌灵残留污染下稻田土壤生态环境的恢复。

Effects of Stenotrophomonas pavanii DJL-M3 on rice rhizosphere microecology under carbendazim stress

Inoculation with agrichemical-degrading endophytes can boost the metabolism of agrichemicals in rice. This beneficial microbe-plant interaction could prove useful for regulating fungicide residues in crop and for the remediation of contaminated farmland. However, the overall effects of introducing functional endophytes on rice rhizosphere microecology under fungicide exposure remain unclear, and the responses of rhizospheric organisms to degrading endophytes should be thoroughly investigated before further application of this symbiotic relationship. Therefore, in this study, we conducted pot experiments to investigate the stress responses of earthworms (Eisenia foetida), soil enzymes, and rhizospheric microorganisms in the rice rhizosphere under carbendazim (CBZ) exposure with and without inoculation with Stenotrophomonas pavanii DJL-M3, which is a CBZ-degrading endophyte. We applied the recommended dosage of CBZ, and then sampled rice rhizosphere soil at regular intervals; soil catalase, soil urease, and sucrose activity were detected immediately, whereas CBZ residue degradation was analyzed using high-performance liquid chromatography (HPLC). After 2 weeks of CBZ exposure, the earthworms were collected and their morphological characteristics were observed; we also detected earthworm malondialdehyde levels and superoxide dismutase and acetylcholine esterase activity in vivo to evaluate the degree of stress damage caused by CBZ contamination. The diversity index and carbon metabolic activity of rhizosphere soil microorganisms were analyzed using an Eco-Plate (Biolog, USA). Rice plants without CBZ treatment and microbial inoculation were used as a background control. The results showed that foliage spraying caused rhizosphere soil exposure with CBZ, which activated soil catalase, but inhibited soil urease and sucrose activity. The CBZ residue in rhizosphere soil led to oxidative damage in earthworms, as demonstrated by the accumulation of malondialdehyde and the overexpression of superoxide dismutase and acetylcholine esterase in vivo. The CBZ contamination significantly reduced the diversity and carbon metabolic activity of rhizosphere soil microorganisms. Within the 14-day experimental period, S. pavanii DJL-M3 inoculation boosted CBZ degradation in the rice rhizosphere by shortening the half-life of CBZ residue, thereby relieving fungicide stress on rhizosphere soil microorganisms and earthworms, as indicated by the enhanced carbon metabolic activity, Shannon index and McIntosh index of rice rhizosphere soil microorganisms, and the recovery of the earthworm survival rate to that of the unpolluted control. This stress relief ultimately significantly promoted soil urease and sucrose activity under CBZ exposure. Therefore, the degrading endophyte S. pavanii DJL-M3 could be used for the bioremediation of CBZ-contaminated paddy soil.